This invention relates to an intake system for an engine and more particularly to an intake system and method for improving the charging efficiency.
Most engines, be they two or four cycle and rotating or reciprocating, employ an intake passage that discharges into a variable volume chamber of the engine and a throttle valve for controlling the flow through the intake passage. Regardless of whether the engine is of the ported or valve type, flow pulsations occur in the intake passage which have the effect of reducing charging efficiency. These problems are particularly prevalent at low to medium engine speeds and/or throttle openings. When the engine intake valve or intake port is open, a charge flows into the chamber. When the valve or port is closed, the flow through the intake passage ceases and the air and charge in effect become stagnent. Thus, during the next opening of the engine valve or port, the inertia of the charge in the intake passage downstream of the throttle valve must be overcome before a charge is again delivered to the chamber. At low engine speeds and low throttle openings, this effect considerably reduces the charging efficiency of the engine. At higher engine speeds the flow in the intake passage becomes more uniform since the greater number of intake cycles in a given period of time causes a flow inertia to develop.
It is, therefore, a principle object of this invention to provide an intake system for an engine in which the charging efficiency, particularly at lower speeds and lower throttle openings, is improved.
It is another object of this invention to provide a method for improving the charging efficiency of an engine.
It is still another further object of this invention to provide a structure or method for improving the charging efficiency of an engine while permitting the maintenance of a compact construction.
It is a further object of this invention to provide a method and structure for the intake system of an engine which not only improves charging efficiency but which also can induce turbulence to the charge introduced to the engine so as to improve combustion efficiency.